Automatic pipette machines or robots are used in the chemical and biological fields to automatically pipette fluids from one place to another, without the need for direct human involvement. Such machines typically load disposable pipette tips from a tip box or tip holder onto a pipette head. Conventional tip boxes generally comprise of a tray with individual holes in which the pipette tips are suspended, and are not designed with the concept of replacing a used tip in the rack. Replacing used tips in the rack has the advantages of eliminating a separate waste container for used tips and allowing the tips to be reused whenever the particular analysis method allows for such reuse. However, by placing a used tip next to an unused tip or next to a tip used to pipette a different fluid, the chance for cross contamination between the tips arises either from direct transfer of fluid through contact between the tips or indirect transfer through splashing from drops falling from the used tips. In addition, some chemical or biological processes require significantly different volumes of fluid to be pipetted at various steps of the analysis, in which case an automated pipetting machine would require different sized pipette tips to transfer the different volumes accurately. However conventional tip boxes accommodate only one volumetric size of pipette tip at a time. If two different pipette tip sizes are needed then two different types of tip box are necessary. This takes tip valuable space on the limited working area of the pipetting machine.
It is desirable to provide a pipette tip holder that reduces that chance of cross contamination of pipette tips so as to enable the reuse of pipette tips in chemical or biological analysis processes. It is also desirable to provide such pipette tip holder that can also accommodate more than one volumetric size of pipette tip, and be relatively easy and inexpensive to fabricate.